1. Field
The present disclosure relates generally to power systems and, in particular, to a method and apparatus for detecting faults in a power system. Still more particularly, the present disclosure relates to a method and apparatus for detecting arc faults in power cables in a power system.
2. Background
Power in the form of electrical energy is used to operate devices in an aircraft. For example, power is used to operate line replaceable units, air conditioners, in-flight entertainment systems, avionics, flight control computers, and other suitable devices in an aircraft.
Power for these different devices may be generated using a power supply. This power may be distributed from the power supply to one or more devices through a power line. The devices receiving power may also be referred to as loads. A power line may be two or more electrical conductors used to transmit electrical power. These conductors may be held together in a sheath and/or some other type of cover.
With these types of power systems, faults may occur with loose connections and/or reduced integrity of the power lines. These faults include hard faults. A hard fault may occur through an open and/or short condition in a power line. Diagnosing this type of fault is generally straightforward.
Intermittent faults, however, may be more difficult to identify. Intermittent faults are faults that may occur periodically and/or randomly. An intermittent fault may include an arcing fault. An arcing fault may occur when power is transferred to a load other than those that are known. For example, a parallel arcing fault may occur when an arc occurs between power lines and the associated return for the power lines. A series arcing fault may occur in which the arc occurs in series with the load. In another example, a ground arcing fault may occur when power arcs from a power line to some other conductor and/or load not part of the power system.
Currently, circuit breakers and ground fault interrupters may not trip for different types of arcs. For example, a circuit breaker does not trip for a series arc, parallel arcs, and/or ground arcs. Ground fault interrupters compare the source in return currents to insure that no leakage of current has occurred. These types of interrupters may protect against a ground arc fault but may not have any effect on a parallel arc fault or a series arc fault.
Another system may involve the use of waveform distortion techniques or direct current feedback techniques for detecting faults. These techniques may rely on an arc causing a change in voltage and/or current. These types of techniques, however, may be susceptible to false alarms. These false alarms may occur due to normal changes in the load and/or environment.
Direct current power lines may employ a direct current feedback technique to identify arcing faults. Arcing faults may be detected by performing differential measurements in the input and load currents and input and load voltages. This type of measurement system, however, may require the use of additional lines and/or cables between the power source and each load. As a result, additional costs, weight, complexity, and reduced system reliability may occur.
Other techniques may involve using sampling blocks to perform current measurements and/or voltage measurements at loads. The sampling blocks return measurements to a processor that may identify faults from the sampled currents and voltages. The information is sent back in the power cables using this type of system.
The use of sampling blocks and sending data through the power cables requires modifications and/or access to the power systems and loads to install the different components. This type of installation may be time consuming and/or expensive.
Therefore, it would be advantageous to have a method and apparatus that takes into account one or more of the issues discussed above, as well as possibly other issues.